Photoelectric elements and electric elements using Group III–V nitride semiconductors are developed actively. Luminescence diode and a laser diode with ultraviolet range or visible range are applied to many fields and their application will be extended more widely in the near future.
It is difficult to grow a nitride semiconductor film and elements of a good quality since nitride substrate of a mono-crystal having a good character is hard to make.
So, conventionally, the nitrides were grown on double-substrates of such as GaAs, ZnO, Sapphire, SiC, etc. Among them, nitride films grown on Sapphire substrate and SiC have specially a good quality enough to be used widely for manufacturing elements.
SiC has a good electric conductivity but very expensive so that most elements are using the nitrides grown on substrate of Sapphire.
Improving the characteristics of the films of the nitride semiconductors is due to the development of growth technology of the nitrides.
In order to grow a nitride film on upper substrate of Sapphire, the Sapphire substrate has to be treated at a high temperature, and then buffer layer is made on it at a low temperature (450˜600° C.). After that, the nitride film is grown on the buffer layer at a high temperature.
During this process, buffer layer growth is important.
FIG. 1 is shown a cross-sectional view of the stacking structure including the nitride semiconductors grown as a conventional method of crystal growth, which comprise the process of growing the buffer layer of the bivalent nitride (11) on the upper substrate of sapphire (10) and the process of growing the layers of the nitride semiconductor (12) on said Group-2 nitride buffer layers.
The necessity of the buffer layer is due to the difference between thermal expansion and the lattice constant of a sapphire substrate and the nitride which grows on the sapphire substrate (10). Namely, to overcome the differences of the thermal expansion and the lattice constant between the nitrides and the sapphire substrate (10), the nitride semiconductor (12) is grown after the layer of bivalent nitride (11) which is selected from GaN, AlN, InN and SiNx or the compounds thereof, is grown on a sapphire substrate (10), as shown FIG. 1.
The nitride film which was grown like the above is not single crystal but polymer or poly crystal so that it can be a seed layer to be able to grow a layer of the nitride compound semiconductor
Using the conventional single buffer layers of such like said GaN, AIN, InN, SiNx, etc., makes the nitride film with an improved characteristics in crystallographical view, but still has lots of problem to overcome the different physical characteristics between sapphire and GaN.
Therefore, in order to get a nitride semiconductor layer with the improved crystalline characteristics a new growth method or development of a new buffer layer is necessary, and this is the core for the improved function of the final product, i.e., elements.
In order to solve the said problems, the present invention provides a method of manufacturing of nitride semiconductor layer with improved electrical and crystalline characteristics by growth the nitride semiconductors on upper substrate of the nitride buffer layer which includes the aluminum.
The present invention provides a method of manufacturing of nitride semiconductor layer comprising: a first step of growing a buffer layer including aluminum on the top of sapphire substrate; a second step of growing bivalent nitride buffer layers on the top of said nitride buffer layers including aluminum; and a third step of growing a nitride semiconductor on the top of said bivalent nitride buffer layers.